Abstract

Two epizootics affecting pilchards Sardinops sagax neopilchardus have been observed over their entire geographical range off the Australian coastline. The first occurred in 1995, involving high mortality (at least 10%) that devastated the pilchard population. The second occurred in 1998 and involved even higher mortality (70%). Both epizootics moved rapidly against the prevailing Leeuwin and East Australian currents from a defined point of origin. A herpesvirus, pilchard herpesvirus (PHV), was determined to be the cause of the epizootics, but the source of the virus remains unknown. In this research, in situ hybridization (ISH), polymerase chain reaction (PCR), and real-time PCR were compared for the detection of PHV in archived paraffin-embedded tissue and frozen tissue collected before, during, and after the 1995 epizootic. Results show that the conventional PCR failed to detect PHV in archived paraffin-embedded tissue, and that real-time PCR was the most sensitive of the 3 techniques and the best method for the detection of PHV.